PROJECT SUMMARY Animal and human studies indicate that extreme forms of early life stress are implicated in structural and functional maladaptation in the brain during the early life course. At the same time, research on developmental psychopathology has indicated that early caregiving and development of insecure or disorganized attachment put children at risk for maladaptive behavioral and emotional problems. Thus, the roots of psychopathology likely take shape during this period of development in the context of transactions between the infant, caregiving environment, and developing brain architecture. Yet, we know little about the potential neurobiological mechanisms linking these transactional processes. Leveraging new methods for assessing infant brain via resting state fMRI and diffusion tensor imaging (DTI), this exploratory/ developmental project aims to explore how integration of neural networks over the first year of life vary as a function of caregiving processes and underlie differences in attachment security/insecurity at the end of the first year. In doing so, we will use longitudinal assessments and multimethod techniques to examine how the quality of infant-mother attachment contributes to intra-network and inter-network connectivity from 3 to 12 months using dynamic whole-brain data-driven approaches. At 3 and 12 months of age, infant scans will be conducted during natural sleep, and resting state functional MRI and DTI will assess changes in functional and structural large-scale network connectivity. At 3, 6, and 9 months, infant-mother interactions will be assessed via (a) an established paradigm that provides age-appropriate assessment of infant attachment-related behavior, and (b) new technology that enables collection of the infant's naturalistic home environment on a large-scale using an automated system that is reliable and valid. At 12 months, infant- mother attachment will be assessed via the gold-standard Strange Situation Procedure. By incorporating multiple levels of analysis across multiple time scales, our project will provide novel insight into transactions among maternal caregiving, infant behavior, and neural networks across the first year of life that underlie infants' attachment-related behavior and representations. Such innovation holds promise for conceptual advances in understanding the role of early caregiving environments in the development of early trajectories of brain and behavior, as well as potential applications for preventive intervention.